Sensory devices based on amplified fluorescence quenching of solid-state conjugated polymer films can be highly sensitive, due to the amplification that arises from delocalized excitons sampling many potential binding sites within one excited state lifetime. Previous work has demonstrated highly sensitive detection schemes using these amplifying fluorescent polymers for a number of analytes in solution and vapor phase, as described in U.S. Publication No. 2003/0178607. For example, sensors for the ultratrace detection of high explosives such as 2,4,6-trinitrotoluene (TNT) have been shown to display high sensitivity comparable to that of trained canines. In many cases, the transduction mechanism is photoinduced charge transfer (PICT) from a polymer donor to a substantially planar analyte that binds via a tight pi-complex to the conjugated polymer. For example, TNT is a planar, nitroaromatic molecule that can readily form a pi-complex with a conjugated polymer via pi-stacking interactions.
Although planar and/or aromatic compounds are often present in many explosives, present day security is in need of systems capable of matching comprehensive vapor phase detection of a broader range of high explosives and toxins. For example, the taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB) is a required additive in all legally manufactured plastic explosives. DMNB has been previously detected using ion mobility spectrometry, a reliable but less sensitive technique relative to amplifying fluorescent polymers. DMNB has also been detected using other methods such as electron capture mass spectrometry which involve bulky and often complex machinery.
Hydrazine (NH2NH2), a heavily used industrial chemical, has been implicated as a carcinogen and is readily absorbed through the skin. Its strong reducing power has led to its use as an oxygen scavenger and corrosion inhibitor in various applications involving water-heating systems, as well as a fuel in rocket propulsion systems. As a result of its toxicity and reactivity, facile detection of hydrazine is also relevant to homeland security. Traditional analytical methods utilized for hydrazine detection include spectrophotometric detection, as well as assorted electrochemical schemes.
Accordingly improved methods are needed.